Galvano mirror unit

ABSTRACT

A galvano mirror unit including a galvano mirror, a mirror holder holding the galvano mirror, and a hinge member which swingably supports the mirror holder. A pair of coils is provided at opposing ends of the mirror holder. A pair of conductive members is provided in the hinge member, so that an electrical signal can be supplied to the coils via the conductive members.

This is a divisional of U.S. patent application Ser. No. 09/492,426,filed Jan. 27, 2000, U.S. Pat. No. 6,344,917, which is a continuation ofU.S. patent application Ser. No. 09/173,678, filed Oct. 16, 1998, nowabandoned the contents both of which are expressly incorporated byreference herein in their entireties.

BACKGROUND OF THE INVENTION

This invention relates to an optical disk drive.

Generally, an optical disk drive is arranged to write and read data onan optical disk by means of a laser beam. The optical disk driveincludes a light source module that emits the laser beam and an opticalhead carrying an objective lens that converges the laser beam on a smalllight spot on the optical disk.

The tracking operation of the optical disk drive includes (1) a roughtracking operation and (2) a fine tracking operation. The rough trackingoperation is accomplished by moving the optical head crossing the tracksof the optical disk. The fine tracking operation is accomplished byminutely moving the light spot on the optical disk. For this purpose, agalvano mirror is provided in a light path between the light sourcemodule and the objective lens. When the galvano mirror is swung by acertain degree, the angle of incidence of the laser beam incident on theobjective lens is changed, so that the light spot on the optical disk ismoved.

Generally, a galvano mirror is mounted to a swingable mirror holder.Coils are provided to opposing ends of the mirror holder. Magnets areprovided to a stationary part of the optical head so that the magnetsare faced with the coils. The galvano mirror is swung by anelectromagnetic induction caused by current flow in the coils and amagnetic field caused by the magnets.

In order to swingably support the mirror holder, it is necessary toprovide a pivoting mechanism such as pivoting shafts and bearings.However, if such a pivoting mechanism is provided to the mirror holder,it may increase the size of a galvano mirror unit (including the galvanomirror, the mirror holder and the pivoting mechanism), particularly inthe direction of a swinging axis of the galvano mirror. Thus, it isdesired to provide a simple arrangement for swingably supporting thegalvano mirror.

Further, in order to connect the coils of the mirror holder to a controlcircuit (provided on the stationary part), wires are laid between themirror holder and the control circuit. Accordingly, when the galvanomirror is swung, the wires also move and may disturb the swinging of thegalvano mirror. Thus, it is desired to provide an electrical feedingpath which does not disturb the swinging of a galvano mirror.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a galvanomirror unit in which a galvano mirror is supported in a simple manner.

Further, it is another object of the present invention to provide agalvano mirror unit in which an electrical feeding path does not disturbthe swinging of a galvano mirror.

According to one aspect of the present invention, there is provided agalvano mirror unit including a galvano mirror, a mirror holder holdingthe galvano mirror, and a hinge member which swingably supports themirror holder. The hinge member includes a support plate and a base. Thesupport plate has a thinner portion extending across the support platein one direction, so that the thinner portion divides the support plateinto first and second sections. The first section is fixed to the mirrorholder, while the second section is supported by the base. The mirrorholder is swingable about the thinner portion, due to an elasticdeformation of the thinner portion.

With such an arrangement, it, is not necessary to provide a pivotingmechanism such as pivoting shafts. Thus, the structure of the galvanomirror unit is simple, which is advantageous in miniaturization of thegalvano mirror unit.

In a particular arrangement, the support plate has a rectangular-shape.The thinner portion is formed in the vicinity of one end of the supportplate and is extended in parallel to the end.

In a preferred embodiment, when the thinner portion is not elasticallydeformed, the first and second sections are aligned on one plane. Theplane is perpendicular to a mirror surface of the galvano mirror.Accordingly, the hinge member is able to resist against the force in thedirection perpendicular to a mirror surface of the galvano mirror.

Advantageously, the mirror holder includes a mirror mounting portion towhich the galvano mirror is mounted, and a recess in which the supportplate is inserted. The recess is located to an opposing side to themirror mounting portion. Since the support plate is inserted in therecess of the mirror holder, a space occupied by the hinge member isrelatively small.

According to another aspect of the present invention, there is provideda galvano mirror holder having a mirror mounting portion to which thegalvano mirror is mounted, a pair of coils provided to opposing ends ofthe mirror holder, and a hinge member which swingably supports themirror holder. The hinge member is located at an opposing side to themirror mounting portion of the mirror holder. With such an arrangement,the hinge member is able to resist against the force in the directionperpendicular to a mirror surface of the galvano mirror.

According to still another aspect of the present invention, there isprovided a galvano mirror unit including a galvano mirror, a mirrorholder holding the galvano mirror, a hinge member which swingablysupports the mirror holder, a pair of coils provided at opposing ends ofthe mirror holder, and a pair of conductive members is provided in thehinge member. Electricity can be supplied to the coils via theconductive members.

With such an arrangement, it is not necessary to fix wires to the mirrorholder. Thus, when the mirror holder swings, the swinging of the mirrorholder is not disturbed by such wires.

In a particular arrangement, the conductive members respectively havecontact surfaces which are exposed to an exterior of the hinge member.The mirror holder has mating surfaces which contact with the contactsurfaces of the conductive members.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is perspective view of an optical disk drive to which first andsecond embodiments of the present invention are embodied;

FIG. 2 is an enlarged view of a floating head of the optical d of FIG.1;

FIG. 3 is an enlarged view of the tip of the rotary arm of the opticaldisk of FIG. 1;

FIG. 4 is a top view of the rotary arm of the optical disk of FIG. 1;

FIG. 5 is a longitudinal sectional view of the rotary arm of the opticaldisk of FIG. 1;

FIG. 6 is a perspective view of a galvano mirror unit according to thefirst embodiment;

FIG. 7 is a perspective view of a hinge member according to the firstembodiment;

FIG. 8 is a horizontal sectional view of the galvano mirror unit of FIG.6;

FIG. 9 is a longitudinal sectional view of the galvano mirror unit ofFIG. 6;

FIG. 10 is a perspective view of a hinge member according to themodification of the first embodiment;

FIG. 11 is a perspective view of a galvano mirror unit according to thesecond embodiment;

FIG. 12 is a perspective view of a hinge member according to the secondembodiment;

FIG. 13 is a partially cutaway view of a galvano mirror unit of 11, withits upper half being removed;

FIG. 14 is a partially cutaway view of a galvano mirror unit of FIG. 11,showing its lower part; and

FIG. 15 is a partially cutaway view of a galvano mirror unit of FIG. 11,showing its upper part.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The embodiments of the galvano mirror unit according to the presentinvention are described below.

First, an optical disk drive in which the first and second embodimentsare embodied is described. FIG. 1 is a perspective view of the opticaldisk drive (hereinafter, the disk drive 1). The disk drive 1 is arrangedto write and read data on an optical disk 2 by means of a so-called NearField Recording (NFR) technology.

In the disk drive 1, the optical disk 2 is mounted to a rotating shaft 2a of a not-shown spindle motor. The disk drive 1 includes a rotary arm 3extending in parallel to a surface of the optical disk 2, and isrotatably supported by a shaft 5. A floating head 6 that carries anoptical lens (described later) is provided to a tip of the rotary arm 3.When the rotary arm 3 is rotated, the floating head 6 moves acrosstracks formed on the optical disk 2. The rotary arm 3 is furtherprovided with a light source module 7 in the vicinity of the shaft 5.

FIG. 2 is an enlarged view of the floating head 6. FIG. 3 is an enlargedview of the tip of the rotary arm 3. As shown in FIG. 3, the floatinghead 6 is mounted to the rotary arm 3 via a flexure beam 8. One end ofthe flexure beam 8 is fixed to the bottom of the rotary arm 3, while thefloating head 6 is fixed to the other end of the flexure beam 8. Whenthe optical disk 2 rotates, the floating head 6 is lifted upward by airflow generated between the optical disk 2 and the floating head 6. Whenthe floating head 6 is lifted upward, the flexure beam 8 is elasticallydeformed, which urges the floating head 6 downward. With this, thefloating amount of the floating head 6 is kept constant, due to thebalance of the upward force (caused by the air flow) and the downwardforce (caused by the deformation of the flexure beam 8).

As shown in FIGS. 2 and 3, the floating head 6 includes an objectivelens 10 and a solid immersion lens (SIL) 11. A reflecting mirror 31 isprovided to the rotary arm 3, which reflects the laser beam 13 emittedfrom the light source module 7 (FIG. 1) to the objective lens 10. Theobjective lens 10 converges the laser beam 13. The solid immersion lens11 is a hemispherical lens and: the plane surface thereof is faced withthe optical disk 2. Further, the focal point of the objective lens 10 ispositioned on the plane surface of the solid immersion lens 11. That is,the laser beam 13 is converged on the plane surface 11 a of the solidimmersion lens 11. Since the clearance of the optical disk and the planesurface 11 a of the solid immersion lens 11 is less than 1 μm, theconverged laser beam is converted to a so-called evanescent beam (whichpropagates across a small gap between closely disposed surfaces) andreaches the optical disk 2. Since the beam diameter of the evanescentbeam is smaller than the converged laser beam, a data storage capacitycan be remarkably increased. The evanescent beam is disclosed in B. D.Terris, H. J. Mamin, and D. Rugar “Near-field optical data storage”,Appl. Phys. Lett., Vol. 68, No. 2, Jan. 8, 1996, teaching of which areincorporated by reference in their entireties.

In order to apply magnetic field on the surface of the optical disk 2, acoil 12 is provided around the solid immersion lens 11. A current flowin the coil 12 generates a magnetic field in which the optical disk 2 ispositioned. Data writing is performed by the evanescent beam from thesolid immersion lens 11 and the magnetic field generated by the coil 12.

FIGS. 4 and 5 are a plan view and a sectional view of the rotary arm 3.As shown in FIGS. 4 and 5, the rotary arm 3 is provided with a drivingcoil 16 at the opposite end to the floating head 6. The driving coil 16is inserted into a not shown magnetic circuit. The driving coil 16 andthe magnetic circuit constitute a voice coil motor 4 (FIG. 1) The rotaryarm 3 is supported by the shaft 5 via bearings 17. When current flows inthe driving coil 16, the rotary arm 3 is rotated about the axis 5, dueto the electromagnetic induction.

As shown in FIGS. 4 and 5, the light source module 7 includes asemiconductor laser 18, a laser drive circuit 19, a collimator lens 20and a composite prism assembly 21. Further, the light source module 7includes a laser power monitor sensor 22, a reflection prism 23, a datasensor 24 and a tracking detection sensor 25. A divergent laser beamemitted from the semiconductor laser 18 is converted to a parallel laserbeam by the collimator lens 20. Due to the characteristics of thesemiconductor laser 18, the sectional shape of the laser beam iselongated. In order to correct the sectional shape of the laser beam, anincident surface 21 a of the composite prism assembly 21 is inclinedwith respect to the incident laser beam. When the laser beam isrefracted by the incident surface 21 a of the composite prism assembly21, the sectional shape of the laser beam becomes a circle. The laserbeam enters a first half mirror surface 21 b. By the first half mirrorsurface 21 b, the laser beam is partially lead to the laser powermonitor sensor 22. The laser power monitor sensor 22 detects theintensity of the incident laser beam. The output from the laser powermonitor sensor 22 is sent to a power control circuit (not shown) so asto stabilize the power of the semiconductor laser 18.

The tracking operation includes two steps: (1) a rough tracking and (2)a fine tracking. The rough tracking is accomplished by the rotation ofthe rotary arm 3. The fine tracking operation is accomplished byminutely moving the light spot on the optical disk 2. For this purpose,a galvano mirror 26 is provided in a light path between the light sourcemodule 7 and the objective lens 10. In particular, the galvano mirror 26is locate so that the laser beam 13 emitted from the light source module7 directly enters. The laser beam 13 reflected by the galvano mirror 26proceeds to the reflection mirror 31 and is reflected (by the reflectionmirror 31) to the floating head 6. Then, the laser beam 13 is convergedand incident on the optical disk 2. By swinging the galvano mirror 26,the incident angle of the laser beam 13 incident on the objective lens10 is changed, so that the light spot on the optical disk 2 is moved.The swinging angle of the galvano mirror 26 is detected by a galvanomirror positioning sensor 28 located in the vicinity of the galvanomirror 26.

When the galvano mirror 26 swings to change the incident angle of thelaser beam 13 incident on the objective lens 10, there is a possibilitythat the laser beam 13 partially fails to enter the objective lens 10.In order to solve this problem, first and second relay lenses 29 and 30are provided between the galvano mirror 26 and the reflection mirror 31to obtain the conjugate relationship between a principal plane of theobjective lens 10 and the center of the mirror surface of the galvanomirror 26 (in the vicinity of the. swinging axis thereof) With this, thelaser beam 13 reflected by the galvano mirror 26 is surely enter theobjective lens 10 irrespective of the swinging of the galvano mirror 26.

The laser beam 13 that has returned from the surface of the optical disk2 travels through the floating head 6, the relay lenses 30 and 29 andthe galvano mirror 26. Then, the laser beam 13 enters the compositeprism assembly 21 and is reflected by the first half mirror surface 21 bto the second half mirror surface 21 c. The laser beam that transmitsthe second half mirror surface 21 c is directed to the trackingdetection sensor 25. The tracking detection sensor 25 outputs a trackerror signal based on the incident laser beam. The laser beam that hasreflected by the second half mirror surface 21 c is split by a Wollastonpolarizing prism 32, generating two polarized beams. The polarized beamsare converged (by a converging lens 33) on the data detection sensor 24via reflection prism 23. The data detection sensor 24 has two lightreceiving portions which respectively receives two polarized beams. Withthis, the data detection sensor 24 reads data recorded on the opticaldisk 2. In particular, the data signal from the tracking detectionsensor 25 and data detection sensor 24 are generated by a not-shownamplifier circuit and sent to a not-shown control circuit.

FIG. 6 is a perspective view of a galvano mirror unit according to thefirst embodiment. The galvano mirror 26 is mounted to a mirror holder100. The mirror holder 100 is supported by a hinge member 110 so thatthe mirror holder 100 is swingable about a swinging axis Z. Hereinafter,the direction in parallel to the swinging axis Z is referred to as avertical direction. Further, a plane that is perpendicular to theswinging axis Z is referred to as a horizontal plane. Further, thegalvano mirror 26 side of the mirror holder 100 is referred to as‘front’, while the opposite side of the mirror holder 100 is referred toas ‘rear’.

As shown in FIG. 6, a pair of coils 121 and 122 are provided to lateralside ends of the mirror holder 100. Further, a pair of magnets 125 and126 are provided on the rotary arm 3 (FIG. 4). The magnets 125 and 126generate a magnetic field in which the coils 121 and 122 are 13positioned. positioned. Lead wires of coils 121 and 122 are respectivelyconnected to terminals 91 and 92 provided on a top surface of the mirrorholder 100. The terminals 91 and 92 are connected to a not-shown controlcircuit via not-shown wires. When current flows in the coils 121 and122, the mirror holder 100 is swung about the swinging axis Z due to theelectromagnetic induction caused by the current and the magnetic field.With such an arrangement, the galvano mirror 26 can be swung thereby tochange the direction of the laser beam reflected by the galvano mirror26.

The mirror holder 100 is provided with a mirror holding recess 102provided between the coils 121 and 122. The galvano mirror 26 is mountedto the mirror holding recess 102 so that its mirror surface directs tothe exterior of the mirror holding recess 102. The mirror surface ofthe. galvano mirror 26 (mounted to the mirror holder 100) is parallel tothe swinging axis Z. Further, the swinging axis Z is located at thelateral center of the galvano mirror 26 when seen from the front.

FIG. 7 is a perspective view of the hinge member 110. The hinge member110 is T-shaped, including vertically provided two rectangular plates: abase plate 111 and a support plate 112. The base plate 111 is supportedon an arm base B (FIG. 9) of the rotary arm 3 (FIG. 4). The supportplate 112 extends from the lateral center of the base plate 111. Thesupport plate 112 of the hinge member 110 has a certain height H and acertain width W. Further, the support plate 112 has a thinner portion113 which is thinner than the remaining portion of the support plate112. The thinner portion 113 is formed at the vicinity of a tip 114 ofthe support plate 112. The thinner portion 113 extends vertically acrossthe support plate 112. Due to the elastic deformation of the thinnerportion 113, the tip 114 of the support plate 112 is swingable withrespect to the remaining portion of the support plate 112.

FIGS. 8 and 9 are a horizontal sectional view and a longitudinalsectional view of the galvano mirror unit. As shown in FIG. 8, themirror holder 100 has a rear recess 103 at an opposing side to themirror mounting recess 102. The rear recess 103 has height and widthsuch that the support plate 112 of the hinge. 110 is inserted therein.The rear recess 103 has a depth (that is, a dimension in the front-reardirection) such that the swinging axis Z is positioned in the recess103. A vertically extending groove 104 a is formed on a surface 104 ofthe rear recess 103. The support plate 112 is inserted in the rearrecess 103, and the tip 114 of the support plate 112 fits into thevertically extending, groove 104 a. With this, the mirror holder 100 ismounted to the hinge member 110. The mirror holder 100 mounted to thetip 114 of the support plate 112 is swingable with respect to theremaining portion of the support plate 112 and the base plate 111. Asshown in FIG. 9, the thinner portion 113 of the support plate 112 isaligned with the swinging axis Z.

With such an arrangement, the mirror holder 100 is supported by thehinge member 110 so that the mirror holder 100 is swingable about theswinging axis Z. When the mirror holder 100 swings from a neutralposition (in which the support plate 112 straightly extends), the mirrorholder 100 is biased toward its neutral position by the elastic force ofthe thinner portion 113.

Further, when the mirror holder 100 is at the neutral position, themirror holder 100 is supported by the hinge member 111 from the back.With this, the mirror holder 100 is able to resist against the force(shown by an arrow F in FIG. 8) in the direction perpendicular to themirror surface of the galvano mirror 26. Further, since the tip 114 ofthe support plate 112 abuts the mirror holder 110 along the verticaldimension of the galvano mirror 26, the inclination of the galvanomirror 26 is prevented.

As constructed above, according to the first embodiment, the galvanomirror 26. (and the mirror holder 100) can be supported in a simplestructure.

FIG. 10 is a perspective view of a hinge member 150 according to amodification of the first embodiment. In this modification, a thinnerportion 153 of a support plate 152 of the hinge member 150 has anopening 153 b formed in the longitudinal center thereof. Two bridgingportions 153 a are formed on upper and lower sides of the opening 153 b.Other structure of the hinge member 150 (except the thinner portion 153)is the same as the hinge member 110 of the first embodiment. The mirrorholder 100 (FIG. 6) is mounted to the tip of the support plate 152 ofthe hinge member 150, so that the mirror holder 100 is swingable aboutthe thinner potion 153.

Due to the existence of the opening 153 b, the elastic force of thethinner portion 153 is weak (compared with the first embodiment). Thus,the mirror holder 100, can be swung by a relatively light force.

The second embodiment of the present invention is described. FIG. 11 isa perspective view of the galvano mirror unit of the second embodiment.In FIG. 11, parts having the same structure as the first embodiment aredenoted by same reference numbers.

As shown in FIG. 11, the mirror holder 100 is not provided withterminals such as the terminals 91 and 92 (FIG. 6) of the firstembodiment. Instead, electrical feeding paths (for feeding electricityto the coils 121 and 122) are provided in the hinge member 110 asdetailed below.

FIG. 12 is a perspective view of the hinge member 110 of the secondembodiment. The hinge member 110 is made of insulation material. Thehinge member 110 is provided with two band-shaped conductive members 141and 142 extending through the interior of the base plate 111 and thesupport plate 112. The conductive members 141 and 142 are located at theupper and lower portions thereof and extend from the rear side of thebase plate 111 to the tip 114 of the support plate 112. The conductivemembers 141 and 142 are made of copper foils or copper wires. At the tip114 of the support plate 112, the conductive members 141 and 142 areexposed to the exterior, which respectively form contact surfaces 141 aand 142 a. Further, at the rear surface of the base plate 111, theconductive members 141 and 142 are exposed to the exterior, whichrespectively form connector surfaces 141 b and 142 b.

FIG. 13 is a partially cutaway view of the galvano mirror unit, with itsupper half being removed. FIG. 14 is a partially cutaway view showing alower part of the galvano mirror unit. The mirror holder 100 is made ofinsulating material. As shown in FIG. 13, the right coil 121 has firstand second lead wires 121 a and 121 b. Similarly, the left coil 122 hasfirst and second lead wires 122 a and 122 b. The second lead wires 121 band 122 b are drawn to the front surface of the mirror holder 100 andattached to a common terminal 109 (by soldering 108) formed on the frontsurface of the mirror holder 100. With this, the coils 121 and 122 areelectrically connected with each other.

As shown in FIG. 13, the first lead wire 121 a of the right coil 121 isdrawn to the inner surface of the rear recess 103 and is soldered to aconductive pattern 131 formed on the inner surface of the rear recess103. As shown in FIG. 14, the conductive pattern 131 extends to thevertically extending groove 104 a so that the conductive pattern 131contacts the contact surface 141 a of the conductive member 141. Withthis, the right coil 121 and the conductive member 141 are electricallyconnected.

FIG. 15 is a partially cutaway view showing the upper portion of thegalvano mirror unit. The first lead wire 122 a (FIG. 13) of the leftcoil 122 is drawn to the inner surface of the rear recess 103 and issoldered to the conductive pattern 132 formed on the inner surface ofthe rear recess 103. The conductive pattern 132 extends to thevertically extending groove 104 a so that the conductive pattern 132contacts the contact surface 142 a of the conductive member 142. Withthis, the left coil 122 and the conductive member 142 are electricallyconnected.

With such an arrangement, (1) the conductive member 141, (2) theconductive pattern 131, (3) the right coil 121, (4) the common terminal109, (5) the left coil 122, (6) the conductive pattern 132 and (7) theconductive member 142 are connected in series. Since the mirror holder100 and the hinge member 110 are made of insulating material, ashort-circuit is prevented. By connecting the connector surface 141 band 142 b to a not-shown control circuit by means of not-shown wires, itbecomes possible to supply electricity to the coils 121 and 122.

As described above, according to the second embodiment, it is notnecessary to fix wires to the mirror holder 100. Thus, the swinging ofthe galvano mirror 26 is not disturbed by the wires.

Although the galvano mirror unit of the present invention is describedherein with respect to the preferred embodiments, many modifications andchanges can be made without departing from the spirit and scope of theinvention.

The present disclosure relates to subject matters contained in JapanesePatent Application Nos. HEI 9-303560, filed on Oct. 17, 1997 and HEI9-303561, filed on Oct. 17, 1997 which are expressly incorporated hereinby reference in their entirety.

What is claimed is:
 1. A galvano mirror unit, comprising: a galvanomirror; a mirror holder holding said galvano mirror; a hinge memberwhich swingably supports said mirror holder; a pair of coils provided atopposing ends of said mirror holder; and a pair of conductive membersprovided in said hinge member, wherein electricity can be supplied tosaid coils via said conductive members.
 2. The galvano mirror unitaccording to claim 1, said conductive members respectively havingcontact surfaces which are exposed to an exterior of said hinge member.3. The galvano mirror unit according to claim 2, said mirror holderhaving mating surfaces which contact with said contact surfaces of saidconductive members.
 4. The galvano mirror unit according to claim 1,wherein said hinge member is made of insulation material.
 5. The galvanomirror unit according to claim 1, wherein said mirror holder is made ofinsulation material.